Recursive makefiles

Another feature of make concerns the environment and recursive invocations. If the sequence $(MAKE) appears anywhere in a shell command line, the line is executed even if the -n flag is set. Since the -n flag is exported across invocations of make (through the MAKEFLAGS variable), the only thing that is executed is the make command itself. This feature is useful when a hierarchy of makefiles describes a set of software subsystems. For testing purposes, make -n can be executed and everything that would have been done will be printed including output from lower-level invocations of make.